The present invention relates to fuel filler necks for motor vehicle fuel tanks and more particularly relates to such filler neck assemblies of the type wherein it is desired not to have a cap or closure on the upper or fuel dispensing nozzle receiving end of the filler neck.
In the design and manufacture of motor vehicles it has become commonplace to provide a fuel filler access door on the outer surface of the vehicle and to provide the fuel dispensing nozzle end of the tank filler neck within a closed cavity formed in the vehicle body structure. Typically the filler neck cavity is accessible through a hinged filler door provided in the exterior of the vehicle body. In such arrangements, the filler neck closure or cap is relied upon for sealing the filler neck to prevent escape of fuel vapors to the atmosphere. However, if, after removal of the cap for refueling the user does not reinstall the cap properly or not completely tight, a not altogether infrequent occurrence, fuel vapors are permitted to escape to the atmosphere.
Currently most fuel filler neck installations employ a bulkhead or partition within the filler neck having an aperture sized to receive the nozzle for only the appropriate fuel, the aperture being closed by a non sealing trap door or spring biased flapper when the dispensing nozzle is removed.
It has been proposed to eliminate the cap on the fuel filler tube or neck and to rely on the biased flapper for automatically sealing the filler tube when the refueling operation has been completed and the nozzle withdrawn from the filler tube. The proposal is complicated by the tendency of the fuel to "spray-back" when a refueling nozzle is inserted in the filler tube for refueling with liquid fuel trapped above the bulkhead by the flapper and residual vapor pressure present in the tank.
Thus, it has been desired to find a way or means of providing a capless fuel tank filler neck which provides spray-back free venting from a pressurized tank condition when a refueling nozzle is inserted in the filler tube. This same structure must provide an air inlet path to support the refueling nozzle aspirator and a vapor tight seal to atmosphere upon removal of the nozzle from the capless filler tube.